In the art of electrical connectors or electrical interconnection devices for cables and the like, the term cable termination typically means a connector that is or can be used at the end or at an intermediate portion of a cable to connect the conductor or conductors thereof to an external member or members, such as another connector, cable termination, printed circuit board, or the like. Such external member usually is part of or can be connected to at least part of another electrical device, circuit, or the like; in any event, the objective is to effect electrical interconnections of respective circuits, lines, conductors, etc. A cable termination assembly is usually referred to as a combination of a cable termination with an electrical cable. Sometimes the terms cable termination and cable termination assembly equivalently are interchanged, depending on context.
The invention is described in detail below with respect to use of the principles of the invention in a multiconductor cable termination assembly. Such cable termination assembly may be used to connect the conductors of a multiconductor cable, for example, a flat ribbon multiconductor cable (or any other electrical cable) to an external member, e.g., as was noted above. The actual cable termination may take the form of a socket or female connector type structure, a card edge connector, and other forms that are well known, as well as those forms that may be developed in the future.
The discussion below relating to the preferred embodiment of the invention is directed to a multiconductor cable termination assembly. It will be appreciated, nevertheless, that the principles of the invention may be used with a cable having only a single conductor or an assemblage of cables, each having one or more conductors.
Multiconductor electrical cable termination assemblies have been available for a number of years. These cable termination assemblies, in fact, have been available in unassembled form requiring mechanical assembly thereof, which includes the mechanical clamping of the termination properly to secure the various elements of the termination and the cable. These cable termination assemblies also have been available as a permanent preassembled and molded integral structural combination. Examples of such cable termination assemblies are found in U.S. Pat. No. 3,444,506 and in U.S. Pat. No. 4,030,799, respectively.
In both such patents and the techniques disclosed therein, the junctions or connections of contacts with respective conductors of the cable are made by part of the contacts piercing through the cable insulation to engage a respective conductor. Such a connection is referred to as an insulation displacement connection (IDC).
Unfortunately, contamination of the IDC junctions, e.g., due to dirt, corrosion and the like, can detrimentally affect the junctions, e.g., causing a high impedance, an open circuit or the like. The mechanically assembled types of prior cable terminations are particularly susceptible to such consquences. The directly molded cable termination assemblies are less susceptible to contamination because of a molded hermetic seal or near hermetic seal surrounding the junctions of the cable conductors and contacts. Examples of such directly molded cable termination assemblies are presented in U.S. Pat. No. 4,030,799 and in U.S. patent application Ser. No. 901,762, for "Improved Jumper Connector", filed Aug. 28, 1986, the disclosures of which are hereby incorporated in their entireties.
One common aspect of both the mechanically assembled cable termination assemblies and the directly molded type is the required assembling step or steps and the separate parts fabrications. These are labor and time consuming and, thus, are relatively expensive. For example, the mechanically assembled devices require the separate molding of several parts followed by assembling thereof. Even in the directly molded device of the '799 patent, to make a socket connector illustrated therein it is necessary to provide a separately molded cover, to install it over the contacts, and then to secure it, e.g., by ultrasonic welding, to the molded base. It would, of course, be desirable to minimize such mechanical assembly and welding steps and attendant costs. Such elimination of the welding is most desirable because the weld is an area of low strength, and to help assure success of a weld it often is necessary to make the parts of the connector of relatively expensive virgin plastic material.
A number of types of electrical contacts are available for use in electrical connectors. Often the contacts are categorized either as a male contact or as a female contact; and a connector or cable termination using male contacts would be categorized as a male connector while a connector using female contacts would be categorized as a female or socket connector. A typical example of a male contact is that known as a pin contact. A pin contact usually is a relatively rigid straight member that is not particularly compliant relative to a female contact. Pin contacts often are inserted into female contacts to make electrical connections therewith; sometimes pin contacts are inserted into holes in a printed circuit board and usually are soldered in place to connect with printed circuits on the board. Another example effectively of a male contact would be the printed circuit traces or portions on a printed circuit board to which an edge board connector or the like may be connected. A female contact may be of the cantilever type, fork type, box type, resilient wiping type, bow type, and so on. Usually a female contact is relatively resilient and relatively compliant compared to a male contact. When a male contact and a female contact are moved relative to each other or are inserted relative to each other, usually there is some deformation of the female contact in response to engagement with the male contact, and often there is a wiping of the contacts against each other as they are brought together to form an electrical connection therebetween.
One type of female contact, the fork contact, is disclosed in U.S. Pat. No. 4,030,799. A molding method disclosed in such patent is that which sometimes is referred to as insert molding, and such method provides an integral structure of the contacts, cable and strain relief material. For such insert molding method, electrical contacts are placed in a mold, a multiconductor cable is placed relative to the contacts and mold, the mold is closed to effect IDC connections of the cable conductors and contacts and to close the mold cavity, and the molding material then is injected into the mold. The fork contacts mentioned are generally planar contacts in that the major extent thereof is in two directions or dimensions (height and width), and the thickness is relatively small; this characteristic makes the fork contacts particularly useful for insert molding.
Other types of electrical contacts are referred to as three-dimensional contacts. An example is that used in some connectors sold by Minnesota Mining and Manufacturing Company and sometimes referred to as a Hi-Rel contact. Such contact has an inverted U-shape. One leg of the U is connected to a base portion of the contact, which base portion in turn is connected to an IDC portion. The other leg of the U is bent out of the plane of the first leg and base to form a resiliently deformable cantilever contacting portion. The contact ordinarily is placed relative to a socket, cell or chamber into which a pin contact may be inserted to engage the cantilever arm or contacting portion. There are a number of advantages to such three-dimensional contacts, including, for example, the relatively large surface available to engage an inserted pin contact and the relatively large compliance factor allowing a large bending capability of the cantilever contacting portion without overstressing the same.
Such three dimensional contacts have been used in mechanically assembled cable termination assemblies in the past, for the complexities of the assembly housing and the various needs of the contact for alignment and support were not provided in a directly molded cable termination assembly configuration.
For a number of the above and possibly other reasons, then, it is desirable to use IDC connections in a cable termination assembly and to directly mold strain relief material. Problems encountered in attempting to accomplish both such goals include difficulties in providing support of the contact during molding (for both placement accuracy and avoiding damage to the contacting portion of the contact, especially if the contact is of the three dimensional type) and in providing a shut off to prevent strain relief material from reaching and interfering with the contacting portion.